[igraph] functions missing from the igraph C documentation

[Szabolcs Horvát]

Hi,

I noticed that several functions that are otherwise documented within
the source code are missing from the online documentation (and also
from the one built using make html in the development version).

Some examples are igraph_gomory_hu_tree(), igraph_sir(),
igraph_modularity_matrix(), etc.

Are these functions not yet ready for general use, or is the
documentation just omitted by accident?

Szabolcs